What is the E.164 phone number format?

E.164 is the international telephone numbering standard published by the ITU. An E.164 number starts with a plus sign, followed by a country calling code (1 to 3 digits) and the national subscriber number, with no spaces, dashes, or parentheses. The total length, excluding the plus sign, is at most 15 digits.

Why do CRMs and SMS tools require E.164?

E.164 is globally unambiguous: the country code is built in, so the same number means the same thing everywhere. SMS and voice gateways like Twilio, and CRMs that integrate with them, require E.164 because it is the only format that routes correctly across borders and deduplicates cleanly.

Does E.164 include the leading zero of a local number?

No. Many countries write local numbers with a leading trunk zero, such as 020 7946 0958 in the UK. In E.164 that trunk zero is dropped and replaced by the country code, giving +442079460958. Keeping the zero is one of the most common formatting mistakes.

How do I convert a column of messy numbers to E.164?

Sigmera's clean phone numbers tool formats a whole column to E.164 in your browser. You set the default country for numbers that lack a code, and it strips spacing and punctuation, drops trunk zeros, and adds the plus sign — without uploading your file anywhere.

What is E.164 phone number format?

Published June 1, 2026 · Last updated: June 2026

E.164 is the international standard for telephone numbers, defined by the ITU. An E.164 number is written as a leading plus sign, a 1-to-3 digit country calling code, and the national number — no spaces or punctuation — for a maximum of 15 digits total. Example: +14155552671.

The structure of an E.164 number

Every valid E.164 number has the same three parts, in the same order, with nothing between them:

1. The leading plus sign (+). It signals “what follows is a full international number.” The plus is the only non-digit character allowed.
2. The country calling code. One to three digits — 1 for the US and Canada, 44 for the UK, 49 for Germany.
3. The national (subscriber) number. The rest of the number, with any national trunk prefix (often a leading 0) removed.

The whole thing, counting the country code and national number but not the plus sign, is capped at 15 digits. There are no spaces, hyphens, dots, or parentheses anywhere.

Examples

Country	How it's often written	E.164 form
United States	(415) 555-2671	+14155552671
United Kingdom	020 7946 0958	+442079460958
Germany	030 901820	+4930901820

Notice the UK and German examples: the local leading 0 disappears and is replaced by the country code. That trunk zero is for dialing within the country only and is never part of the E.164 form.

Why CRMs and SMS tools demand it

A number like “555-2671” is meaningless without context — which country, which area? E.164 removes that ambiguity by baking the country code into the number itself, so it means exactly one thing anywhere in the world. That property is why:

SMS and voice gateways (Twilio, Vonage, MessageBird) accept E.164 and often nothing else — it is the only format that routes correctly across borders.
CRMs and marketing platforms store phones in E.164 so a number deduplicates cleanly and matches the same contact across systems.
Validation and lookup APIs expect E.164 input, so storing it that way avoids a conversion step on every call.

Common mistakes to avoid

Keeping the national trunk zero after the country code.
Leaving spaces, dashes, or parentheses in the stored value.
Omitting the plus sign — 14155552671 is ambiguous; +14155552671 is not.
Storing numbers without a country code at all, so imports guess wrong.

Convert a whole column of messy numbers to E.164 — in your browser, nothing uploaded.

Clean phone numbers Related topic: formatting phone numbers

Frequently asked questions

What is the E.164 phone number format?: E.164 is the international telephone numbering standard published by the ITU. An E.164 number starts with a plus sign, followed by a country calling code (1 to 3 digits) and the national subscriber number, with no spaces, dashes, or parentheses. The total length, excluding the plus sign, is at most 15 digits.
Why do CRMs and SMS tools require E.164?: E.164 is globally unambiguous: the country code is built in, so the same number means the same thing everywhere. SMS and voice gateways like Twilio, and CRMs that integrate with them, require E.164 because it is the only format that routes correctly across borders and deduplicates cleanly.
Does E.164 include the leading zero of a local number?: No. Many countries write local numbers with a leading trunk zero, such as 020 7946 0958 in the UK. In E.164 that trunk zero is dropped and replaced by the country code, giving +442079460958. Keeping the zero is one of the most common formatting mistakes.
How do I convert a column of messy numbers to E.164?: Sigmera's clean phone numbers tool formats a whole column to E.164 in your browser. You set the default country for numbers that lack a code, and it strips spacing and punctuation, drops trunk zeros, and adds the plus sign — without uploading your file anywhere.